Jet pump apparatus

ABSTRACT

A jet pump apparatus for mixing a higher pressure gas and a lower pressure gas, includes an inlet section, an outlet section, a diffuser section and a mixing section. Inlet section includes a higher pressure inlet and a lower pressure inlet. Mixing section includes a plurality of separated mixing chambers. The diffuser section includes diffusers for receiving mixed gases from the mixing chambers. The outlet section receives mixed gases from the diffuser section and conveys those gases to an outlet. The inlet section includes a higher pressure inlet which receives higher pressure gas, and a lower pressure gas inlet which receives lower pressure gas. Each of the mixing chambers has a primary nozzle for introducing primarily higher pressure gas from to a respective mixing chamber, and a secondary inlet for introducing primarily lower pressure gas to each of the mixing chambers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to United Kingdom Patent ApplicationNo. GB0705361.4 filed Mar. 21, 2007, which is incorporated in itsentirety by reference herein.

BACKGROUND OF THE INVENTION

This invention relates to a jet pump apparatus for mixing a higherpressure gas from a higher pressure gas supply derived from a compressorstage of a gas turbine engine, which typically is an aircraft engine,and a lower pressure gas from a lower pressure gas supply in order toprovide a pressurised gas supply to a downstream apparatus, such as forexample only, a downstream on-board oxygen generating system, e.g. ofthe kind which utilises molecular sieve bed technology, or an airconditioning apparatus, or any other desired gas-using downstreamapparatus.

More particularly but not exclusively the invention is for mixing higherand lower pressure gases which are produced by respective higher andlower compression stages of a gas turbine engine.

DESCRIPTION OF THE PRIOR ART

Jet pumps are known for this purpose. These may alternatively be calledinjectors, airmovers, inducers, inspirators, vacuum pumps, ejectors,pressure exchangers, venturis, etc. These include a mixing chamber towhich higher and lower pressure gas supplies are provided.

The purpose of using a jet pump in this context is to optimise the gassupply to be supplied to the downstream apparatus, for example as thepressure and/or temperatures the higher and lower gas pressure suppliesmay fluctuate.

It has been found that in a conventional jet pump design there ispreferred relationship between the mixing chamber cross section andmixing chamber length for optimum mixing, this relationship commonlybeing expressed where the mixing chamber is of circular cross section,as a ratio between the mixing chamber length and diameter, whichtypically is about 8. Achieving this ratio whilst delivering a desiredtemperature of gas downstream thus places constraints on jet pumpdesign. Particularly, in some applications there is insufficient spaceto accommodate a jet pump with a sufficiently long mixing chamber.

SUMMARY OF THE INVENTION

According to a first aspect of the invention we provide a jet pumpapparatus for mixing a higher pressure gas from a higher pressure gassupply and a lower pressure gas from a lower pressure gas supply. Theapparatus may include an inlet section, an outlet section, a diffusersection and a mixing section, the inlet section including a higherpressure gas inlet and a lower pressure gas inlet, the mixing sectionincluding a plurality of separated mixing chambers, and the diffusersection including diffusers for receiving mixed gases from each of themixing chambers, and the outlet section receiving mixed gases from thediffuser section and conveying the mixed gases to a mixed gas outlet.

The inlet section may include a higher pressure gas inlet duct whichreceives higher pressure gas from the higher pressure gas inlet, and alower pressure gas inlet duct which receives lower pressure gas from thelower pressure gas inlet. For each of the plurality of mixing chambers,there may be a primary nozzle for introducing primary higher pressuregas from the higher pressure gas inlet duct to a respective mixingchamber. There may be a secondary inlet for introducing primarily lowerpressure gas from the lower pressure inlet duct to each of the mixingchambers, the higher pressure gas being derived from a compressorsection of a gas turbine engine.

The invention enables a jet pump apparatus to be provided with aplurality of parallel mixing chambers, each mixing chamber having thepreferred mixing chamber length to mixing chamber cross section ratio,whilst overall the jet pump apparatus may be significantly shorter thana comparable conventionally constructed jet pump which has a singlemixing chamber, whilst being able to provide the same gas supply to adownstream apparatus. This makes the jet pump apparatus of the inventionparticularly useful in contexts where there is restricted space, such asin an aircraft.

Each primary nozzle may have a larger cross section nozzle inlet toreceive primarily higher pressure gas from the higher pressure gas inletduct, and a smaller cross section outlet to deliver the gas to therespective mixing chamber.

In one example the primary nozzles each extend along axes which areparallel to a higher pressure gas flow direction as the higher pressuregas passes through the higher pressure gas inlet into the higherpressure gas inlet duct, and the secondary inlet introduces the lowerpressure gas into the respective mixing chambers in a direction which istransverse to a lower pressure gas flow direction as the lower pressuregas passes through the lower pressure gas inlet and into the lowerpressure gas inlet duct.

However if desired. the primary nozzles may each extend along axes whichare transverse to a higher pressure gas flow direction as the higherpressure gas passes through the higher pressure gas inlet into thehigher pressure gas inlet duct, and the secondary inlet introduces thelower pressure gas into the respective mixing chambers in a directionwhich is parallel to a lower pressure gas flow direction as the lowerpressure gas passes through the lower pressure gas inlet and into thelower pressure gas inlet duct.

Each diffuser of the diffuser section may have a cross section whichincreases from an inlet towards the outlet section.

Where the mixing chambers are each of circular cross section, preferablythese are closely nested e.g. with diffuser exterior walls in contactwith as many as possible of the exterior walls of the other diffusers.It will be appreciated that there may therefore be an axially extendingspacing provided by an actual void or solid body, between the nestedmixing chambers which may continue between the diffusers of the diffusersection. The cross section of the inlet of the outlet section maysubstantially equal the combined cross sections of each of the diffusersat their largest cross section ends, plus the cross section of theaxially extending spacing.

The jet pump apparatus of the invention may be used for supplyingpressurised gas to a downstream apparatus of an aircraft. In oneembodiment, the higher pressure gas inlet may thus be connected to ahigher compression stage of a gas turbine engine, and the lower pressuregas inlet may be connected to a lower compression stage of a gas turbineengine.

According to a second aspect of the invention we provide a compressedgas supply system including a jet pump apparatus in accordance with thefirst aspect of the invention.

According to a third aspect of the invention we provide an aircraftwhich includes the compressed air supply system of the second aspect ofthe invention and a downstream apparatus which receives a pressurisedgas supply from the compressed air supply system, the downstreamapparatus including at least one of an on-board oxygen generating systemand an air conditioning system.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings in which:

FIG. 1 is a diagrammatic side view of a compressed air supply system andjet pump apparatus, in accordance with the present invention;

FIG. 1 a is an end diagrammatic view of the jet pump apparatus of FIG.1;

FIG. 2 is a view similar to FIG. 1 but of another embodiment; and

FIG. 3 is an illustrative view of an aircraft which may embody theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 1 a and 3 of the drawings there is shown acompressed air supply system 10 of an aircraft 100, the system 10receiving compressed bleed air from a gas turbine engine 11, anddelivering pressurised gas to a downstream gas using apparatus 12 suchas for examples only, an on-board oxygen or other product gas generatingapparatus 12, which separates the pressurised gas into product gas andnon-product gas, and/or an air conditioning apparatus of the aircraft100.

The compressed air supply system 10 includes a jet pump apparatus 15which has an inlet section 16, a mixing section 17, a diffuser section18 and an outlet section 19.

The inlet section 16 includes a higher pressure air inlet 22 a which isconnected to a higher compression stage 11 a of the gas turbine engine11, and a lower pressure air inlet 24 a which is connected to a lowercompression stage 11 b of the gas turbine engine 11.

The mixing section 17 is provided by a plurality of mixing chambers 25a-25 d, four in this example, where the higher and lower pressure airsare mixed. The mixing chambers 25 a-25 d each receive both higher andlower pressure air from the inlet section 16, and each communicate witha respective diffuser 18 a-18 d of the diffuser section 18, whichconveys the compressed air to the common outlet section 19 which isconnected to the downstream gas using apparatus 12.

In this example, the mixing chambers 25 a-25 d are each cylindricalhaving a common and constant diameter D. The mixing chambers 25 a-25 dextend generally parallel to one another and there is an axiallyextending spacing 28 between the four mixing chambers 25 a-25 d, whichmay be a void as illustrated or a solid body.

Each mixing chamber 25 a-25 d extends from a mixing plane 29 where theinlet section 16 terminates, to the respective diffuser 18 a-18 d of thediffuser section 18. The diffusers 18 a-18 d are each generally circularin cross section and in this example, each has an inlet 36 a-36 d whichhas a diameter which affords it a cross section which is the same as thecross section of the respective mixing chamber 25 a-25 d. In thisexample the axially extending spacing 28 continues between the diffusers18 a-18 d.

The diameters of the diffusers 18 a-18 d increase along the axialextents of the diffusers 18 a-18 d towards the outlet section 19.

Exterior diffuser walls 26 a-26 d at least at the larger diameter endsof the diffusers 18 a-18 d are in contact in this arrangement, so thatthe mixing chambers 25 a-25 d are as closely nested as possible.

The outlet section 19 is in this example cylindrical, and has an inlet33 which receives the mixed air from each of the diffusers 18 a-18 d.The outlet section inlet 33 diameter is at least as great as thecombined cross sections of the diffusers 18 a-18 d at their largestcross section ends, and this example, the outlet section inlet 33 crosssection equals the combined cross sections of the largest diameter endsof the diffusers 18 a-18 d plus the cross section of the axiallyextending spacing 28.

The outlet section 19 is of generally constant diameter, which in thisexample is substantially the same as the diameter of the lower airpressure inlet 24 a of the inlet section 16. The outlet section 19includes a mixed air outlet 35 which is connected to the downstream gasusing apparatus 12.

The inlet section 16 includes a higher pressure air inlet duct 22 whichreceives the higher pressure air from the higher pressure air inlet 22a, and a lower pressure air inlet duct 24 which receives the lowerpressure air from the lower pressure air inlet 24 a.

The inlet section 16 further includes a plurality of primary nozzles 28a-28 d, four in this example, which each receive the higher pressure airfrom the higher pressure air inlet duct 22 and provide the higherpressure air to a respective mixing chamber 25 a-25 d. Each primarynozzle 28 a-28 d has a respective larger cross section nozzle inlet 30a-30 d to receive the higher pressure air from the higher pressure airinlet duct 22, and a smaller cross section outlet 31 a-31 d to deliverthe higher pressure air to its respective mixing chamber 25 a-25 d. Theprimary nozzles 28 a-28 d in this example extend generally parallel toone another along respective axes which lie transverse to a higherpressure air flow direction A as the higher pressure air passes throughthe higher pressure air inlet 22 a, into the higher pressure air inletduct 22 of the inlet section 16.

The smaller cross section downstream ends of the primary nozzles 28 a-28d terminate just upstream of the mixing plane 29.

The inlet section 16 further includes a secondary inlet 34 which in thisexample is defined between the primary nozzles 28 a-28 d, the secondaryinlet 34 receiving lower pressure air from the lower pressure air inletduct 24. The secondary inlet 34 communicates with each of the mixingchambers 25 a-25 d. The secondary inlet 34 is generally in line with thelower air pressure inlet 24 a to the inlet section 16. Thus thesecondary inlet 34 introduces the lower pressure gas into the mixingchambers 25 a-25 d in a direction which is generally parallel to a lowerpressure air flow direction B as the lower pressure air passes throughthe lower pressure air inlet 24 a into the lower pressure air inlet duct24.

It can be seen that the cross section of the lower air pressure inlet 24a is larger than the cross section of the higher pressure air inlet 22a. The inlet section 16 geometry shown and described results in thehigher pressure air entering the respective mixing chambers 25 a-25 dthrough the primary nozzles 28 a-28 d whilst primarily the lowerpressure air enters the mixing chambers 25 a-25 d through the secondaryinlet 34.

As is well known to a person skilled in the art, the reducing crosssections of primary nozzles 28 a-28 d in the direction of air flow,creates a jet effect to draw the lower pressure air into the secondaryinlet 34. The pressurised air from the engine 11 will be at hightemperature. The lower pressure air from the lower compression stage 11b will be cooler than the more highly compressed air from the highercompression stage 11 a of the engine 11.

To avoid or reduce the need to cool the mixed air in a downstream aircooler, desirably lower pressure air would primarily be used. However,although the lower pressure air is compressed, greater pressure air isdesirable.

The jet pump apparatus 15 described allows high pressure air A toupgrade the pressure of the mixed air, compared with a solely lowerpressure air supply B from compressor stage 11 b of the engine 11. Thusless hot higher pressure air A is required, which also is a moreeconomic and efficient arrangement than using solely hotter highercompression air A.

Also in the event of any reduction in the pressure of the availablelower pressure air supply B, the higher pressure air supply A willmaintain adequate pressure downstream of the apparatus 15.

Each mixing chamber 25 a-25 d preferably has a length to diameter ratioof substantially 8, which it is well known, results in the mostefficient mixing of the different pressure gases.

The geometry of the jet pump apparatus 15 described providesfunctionally, four jet pumps, but with common inlet 16 and outlet 19sections. The apparatus 15 is significantly shorter in overall lengththan would be an equivalent single mixing chamber jet pump fordelivering the same mixed air supply to the downstream gas usingapparatus 12, whilst the preferred relationship between the mixingchamber length to cross section, expressed in this example as the lengthto diameter ratio of 8, which would be required in a single mixingchamber arrangement, is preserved for each of the multiple mixingchambers 25 a-25 d of the jet pump apparatus 15 described.

Accordingly the jet pump apparatus 15 may be used in applications wherethere is insufficient space to accommodate a longer single mixingchamber jet pump, e.g. in an aircraft 100 context.

Referring to FIG. 2, a compressed air supply system 10 is shown which isvery similar to that of FIG. 1, but in this case the inlet section ismodified. The same references are used in FIG. 2 for parts correspondingto those shown in FIG. 1. In FIG. 2, the engine 11 is not shown.

Whereas in the FIG. 1 embodiment, the higher pressure air A passesthrough the higher pressure air inlet 22 a into the higher pressure airinlet duct 22 in a direction A transverse to the elongate axes of theprimary nozzles 28 a-28 d, and the lower pressure air B passes throughthe lower pressure air inlet 24 a into the lower pressure air inlet duct24 a direction B parallel to the direction in which the lower pressureair is introduced through the secondary inlet 34 into the mixingchambers 25 a-25 d, in FIG. 2 an opposite arrangement is adopted.

In FIG. 2, the higher pressure air passes though the higher pressure airinlet 22 a into the higher pressure air inlet duct 22 in a directionparallel to the elongate axes of the primary nozzles 28 a-28 d, and thelower pressure air B passes though the lower pressure air inlet 24 ainto the lower pressure air inlet duct 24 in a direction transverse tothe direction in which the lower pressure air is introduced into themixing chambers 25 a-25 d. In this embodiment, preferably the lowerpressure air passes through the lower pressure air inlet 34, via inletconduits 34 a and 34 c, tangentially of the primary nozzles 28 a-28 d.

Various modifications may be made without departing from the scope ofthe invention.

Although in this example, four mixing chambers 25 a-25 d are provided,in another example two, three or more than four mixing chambers 25 a-25d may be provided to achieve a desired mixed air supply with a jet pumpapparatus shorter than an equivalent single mixing chamber jet pump.

The mixing chambers 25 a-25 d need not be circular in cross section asdescribed, although this is a preferred configuration, provided that thepreferred mixing chamber length to cross section relationship ismaintained. Similarly the outlet section 19 need not be circular incross section, and the diffusers 18 a-18 d for each of the mixingchambers 25 a-25 d need not be frusto-conical as shown and described,although again, this is a preferred configuration.

The multiple mixing chambers 25 a-25 d and their diffusers 18 a-18 dneed not be nested as illustrated, particularly where a differentmultiple number of mixing chambers 25 a-25 d are provided than the fourin the example. Preferably the exterior wall 26 a-26 d of each diffuser18 a-18 d will be in contact with or at least as close as is practical,to as many other exterior diffuser walls 26 a-26 d as is possible, so asto provide a smooth transition for the mixed air from the diffusers 18a-18 d into the outlet section 19, and so that the outlet section 19cross section can be the same as or at least similar to the crosssection of the lower pressure air inlet 24.

As described, the primary nozzles 28 a-28 d and are all offrusto-conical configuration, which is preferred, but may be of othersuitable configurations. The secondary inlet 34 may be providedotherwise than between the primary nozzles 28 a-28 d as in the exampledescribed.

In the examples, the higher pressure air from the higher compressionstage 11 a of the engine 11 enters the inlet section 16 in a direction Awhich is transverse to the direction in which the lower pressure airfrom the lower compression stage 11 b of the engine 11 enters the inletsection 16, indicated at B. Preferably these airs enter the inletsection 16 in relatively transverse directions, but in another design,these may enter the inlet section 16 in the same or generally the samedirection.

The jet pump apparatus 15 described may be readily fabricated orotherwise made, in metal or another suitable material.

The invention has been described with reference to an embodiment inwhich the higher and lower pressure gases to be mixed are air, but theapparatus 15 may be used to mix other gases as required, even dissimilarhigher and lower pressure gases, depending on the requirements of thedownstream apparatus 12 to be fed with the gas, which may be any gasusing apparatus.

The lower pressure gas supply need not be derived from the gas turbineengine 11 at all, but could for example, be ambient air which may bepressurised as a result of the aircraft's 100 movement through the air.

The jet pump apparatus 15 in the example is described for use in anaircraft 100, but of course the apparatus 15 has multifarious other usesin vehicular, and static applications. In each case though, the higherpressure air supply is derived from the compressor section of a gasturbine engine.

The invention claimed is:
 1. A jet pump apparatus for mixing a higherpressure gas from a higher pressure gas supply and a lower pressure gasfrom a lower pressure gas supply, the apparatus including an inletsection, an outlet section, a diffuser section and a mixing section, theinlet section including a higher pressure gas inlet and a lower pressuregas inlet, the mixing section including a plurality of separated mixingchambers, and the diffuser section including diffusers for receivingmixed gases from each of the mixing chambers, and the outlet section forreceiving mixed gases from the diffuser section and conveying the mixedgases to a mixed gas outlet, and the inlet section including a higherpressure gas inlet duct which receives higher pressure gas from thehigher pressure gas inlet, and a lower pressure gas inlet duct whichreceives lower pressure gas from the lower pressure gas inlet, and foreach of the plurality of mixing chambers, there being a primary nozzlefor introducing primarily higher pressure gas from the higher pressuregas inlet duct axially into a respective mixing chamber, and there beinga secondary inlet for introducing primarily lower pressure gas from thelower pressure inlet duct axially into each of the mixing chambers, thehigher pressure gas being derived from a compressor section of a gasturbine engine, wherein each of the diffusers of the diffuser sectionhas a cross section which increases towards the outlet section; whereinthe mixing chambers are each of circular cross section, and the mixingchambers are closely nested so that there is an axially extendingspacing between the nested mixing chambers; and wherein exterior wallsof adjacent diffusers at least at the larger diameter end of thediffuser are in contact.
 2. An apparatus according to claim 1 whereinthe plurality of mixing chambers are arranged generally parallel to eachother.
 3. An apparatus according to claim 1 wherein the mixing chambersare generally cylindrical, each mixing chamber having a mixing chamberlength to mixing chamber diameter ratio of about
 8. 4. An apparatusaccording to claim 1 wherein each primary nozzle has a larger crosssection nozzle inlet to receive primarily higher pressure gas from thehigher pressure gas inlet duct, and a smaller cross section outlet todeliver the gas to the respective mixing chamber.
 5. An apparatusaccording to claim 1 wherein the primary nozzles each extend along axeswhich are parallel to a higher pressure gas flow direction as the higherpressure gas passes through the higher pressure gas inlet into thehigher pressure gas inlet duct, and the secondary inlet introduces thelower pressure gas into the respective mixing chambers in a directionwhich is transverse to a lower pressure gas flow direction as the lowerpressure gas passes through the lower pressure gas inlet into the lowerpressure gas inlet duct.
 6. An apparatus according to claim 1 whereinthe primary nozzles each extend along axes which are transverse to ahigher pressure gas flow direction as the higher pressure gas passesthrough the higher pressure gas inlet into the higher pressure gas inletduct, and the secondary inlet introduces the lower pressure gas into therespective mixing chambers in a direction which is parallel to a lowerpressure gas flow direction as the lower pressure gas passes through thelower pressure gas inlet into the lower pressure gas inlet duct.
 7. Anapparatus according to claim 1 wherein the cross section of an inlet ofthe outlet section substantially equals the combined cross sections ofeach of the diffusers at their largest cross section ends, plus thecross section of the axially extending spacing.
 8. An apparatusaccording to claim 1 wherein the higher pressure gas inlet is connectedto a higher compression stage of the gas turbine engine, and the lowerpressure gas inlet is connected to a lower compression stage of the gasturbine engine.
 9. A compressed gas supply system including a jet pumpapparatus of claim 1 for mixing a higher pressure gas from a higherpressure gas supply and a lower pressure gas from a lower pressure gassupply.
 10. A compressed gas supply system according to claim 9 wherein,in the jet pump apparatus, the primary nozzles each extend along axeswhich are parallel to a higher pressure gas flow direction as the higherpressure gas passes through the higher pressure gas inlet into thehigher pressure gas inlet duct, and the secondary inlet introduces thelower pressure gas into the respective mixing chambers in a directionwhich is transverse to a lower pressure gas flow direction as the lowerpressure gas passes through the lower pressure gas inlet into the lowerpressure gas inlet duct.
 11. A compressed gas supply system according toclaim 9 wherein, in the jet pump apparatus, the primary nozzles eachextend along axes which are transverse to a higher pressure gas flowdirection as the higher pressure gas passes through the higher pressuregas inlet into the higher pressure gas inlet duct, and the secondaryinlet introduces the lower pressure gas into the respective mixingchambers in a direction which is parallel to a lower pressure gas flowdirection as the lower pressure gas passes through the lower pressuregas inlet into the lower pressure gas inlet duct.
 12. An aircraft whichincludes a compressed air supply system including a jet pump apparatusof claim 1 for mixing a higher pressure gas from a higher pressure gassupply and a lower pressure gas from a lower pressure gas supply.
 13. Anaircraft according to claim 12 wherein, in the jet pump apparatus, theprimary nozzles each extend along axes which are parallel to a higherpressure gas flow direction as the higher pressure gas passes throughthe higher pressure gas inlet into the higher pressure gas inlet duct,and the secondary inlet introduces the lower pressure gas into therespective mixing chambers in a direction which is transverse to a lowerpressure gas flow direction as the lower pressure gas passes through thelower pressure gas inlet into the lower pressure gas inlet duct.
 14. Anaircraft according to claim 12 wherein, in the jet pump apparatus, theprimary nozzles each extend along axes which are transverse to a higherpressure gas flow direction as the higher pressure gas passes throughthe higher pressure gas inlet into the higher pressure gas inlet duct,and the secondary inlet introduces the lower pressure gas into therespective mixing chambers in a direction which is parallel to a lowerpressure gas flow direction as the lower pressure gas passes through thelower pressure gas inlet into the lower pressure gas inlet duct.